This invention relates to a process for the production of a recording material consisting of a flexible layer support in the form of a tape and one or more photographic or magnetic layers cast on this tape and optionally one or more layers cast on the other side of the layer support.
Polyethylene terephthalate (polyester) is the material nowadays preferably used for the layer support for the production of recording materials of the type mentioned above, such as photographic films or magnetic tapes. The thickness of the layer support depends on the purpose for which it is used and is generally about 3 to 500 .mu.m. Numerous processes for the production of such layer supports are known, for example from GB Applications 99 54 38, 95 42 04 and 87 00 95, WO Application 85 00 1247, DE-OS 1 097 704, 2 219 363, 3 201 153 and 3 333 703 and EP O 099 839 and 0 160 889.
It is clear from the above-mentioned specifications that to produce polyester layer supports having the required mechanical properties, the supports must be stretched both transversely and in the longitudinal direction under specified thermal conditions. This necessitates an enormously complicated and expensive manufacturing process.
Further disadvantages of such layer supports are:
The difficulty of avoiding inhomogeneity due among other things to the high viscosity of the polyester melt in the casting process. especially when thin films are to be produced, PA1 three-dimensional film profiles, especially variations in thickness due to the complicated method of production, PA1 severe wear on the cutting tools used for cutting the recording materials to the width required for use, and PA1 high manufacturing costs since the layer support must be wound and tested after its production before casting can be continued.
The problem therefore arose of finding a process for the production of a recording carrier of the type mentioned above which would not have the aforesaid disadvantages and which in particular would enable the required coatings to be applied with known casting apparatus on line immediately after the production of the layer support.
According to the invention, this problem was solved by a process having the features mentioned in the characterising part of claim 1. Further details of the invention will be apparent from the sub-claims, the description and the drawings.